[throwusawayus]

innodb supports cross-schema foreign keys, there’s no limitation to tables in a single database

can be terrible in mysql 8 though due to metadata locks now extending across foreign key boundaries. this means alter in one schema can block things in other schema if foreign key across databases

speaking of, am surprised that blog post author doesnt discuss the new mysql 8 metadata locking behavior, is new major problem with mysql foreign keys!

[frazerclement]

You are right about cross schema foreign keys being supported, my mistake.